It is known that a photographic material for a color-diffusive transfer method (the so-called instant photography), a heat-development color-diffusive transfer method and a method employing a photosensitive microcapsule are known as a method for forming an image wherein a photosensitive silver halide is exposed and developed to form or release and diffuse an image-forming dye followed by transfer of the dye to form an image.
Images obtained according to these methods are generally poor in fastness to light as compared with those obtained according to conventional photographic methods so that a variety of methods have been proposed hitherto for enhancing fastness to light.
Mentioned as one of the methods is the use of a UV-absorbing agent. This method comprises decreasing the light quantity irradiated to a color image by the UV-absorbing agent to enhance fastness to light. As a matter of course, however, this method inhibited fading due to ultraviolet light but utterly failed to inhibit fading due to visible light. In addition, a problem arises in fading or discoloring of an image caused by the UV-absorbing agent.
It is secondarily or incidentally necessary to use a relatively large amount of a UV-absorbing agent to sufficiently improve the fastness to light. The use of a large amount of UV-absorbing agent results in an increase of film thickness so that it causes a problem such as increase in transfer time, deterioration of resolution and poor turn of processing as well as a problem such as deterioration of film strength and precipitation of the UV-absorbing agent.
What is more, the effect of a fluorescent brightening agent is lowered to decrease whiteness and the like principle problem, thus failing to impart sufficient fastness to light to an image.
A discussion is also made on various fade-preventing agents employed in the so-called conventional photographic system. However, the fade-preventing agents useful in the conventional photographic system are oil-soluble. On the other hand, dyes used in the photographic method of the present invention wherein the dyes are transferred to form images are chiefly water-soluble. Accordingly, a satisfactory effect could not be achieved in the present invention wherein the fade-preventing agents were absent in a position where they could sufficiently react with the dyes on account of the layer construction.
In the dye-diffusive transfer system, effective fade-preventing agent are disclosed in JP-A-62-1441 ("JP-A" means unexamined published Japanese patent application). The invention in the publication discloses dye image receiving materials containing piperidines in color diffusion-transfer photography, but fails to disclose radicals and could not achieve sufficient effects.
As another invention, JP-B-49-20974 ("JP-B" means examined Japanese patent publication) discloses addition of hindered piperidines and/or radicals thereof to a photosensitive material and also discloses that the effect is also attained in the dye-diffusive transfer method. In case these additives are added directly to a dye-fixing element, however, color mixing will be generated and photographic characteristic change will also take place, thus failing to obtain a good color image.